1. scub the mussels under cold running water to remove any mud. Using a sharp knife, cut away the feathery "beards" from the shells. Discard any open mussels that do not shut when tapped sharply with a knife. Rinse again in cold water.

2. Place the lager, onions, garlic, chili, and tomatoes in a heavy based pan. Bring to a boil.

3. Add the mussels and cook, covered, over a medium high heat for about 10 minutes until the shells open. Discard any mussels that do not open.